Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Constriction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources
PubMed1995

Chylothorax associated with constrictive pericarditis in a dog.

Chylothorax was associated with constrictive pericarditis in a 6-year-old mixed-breed dog. Clinical signs included hepatomegaly, bilateral jugular pulses, muffled heart sounds, and dyspnea. Pleural effusion was identified on thoracic radiographs. Thoracentesis yielded 3 L of chylous effusion, confirmed by the cholesterol/triglyceride ratio (0.14). Echocardiography revealed a thickened pericardium, with numerous fibrin tags, which was suggestive of constrictive pericarditis. Central venous, right atrial, and right ventricular pressures were high and on right ventricular diastolic pressure tracings, the square-root sign, which is indicative of constrictive pericarditis, was evident. Exploratory thoracotomy and pericardiectomy were performed. Histopathologic findings were consistent with chronic non-suppurative pericarditis. The dog's condition improved after surgery. On reevaluation 11 months later, central venous pressure and results of physical examination and thoracic radiography were normal. On the basis of these findings, we concluded that chylothorax was caused by constrictive pericarditis in this dog. Chylothorax is often associated with disorders that have a poor prognosis, but if constrictive pericarditis can be identified as the cause of the chylothorax, exploratory thoracotomy and pericardiectomy can provide a cure.

Animals↗
PubMed1994

[Radiation-induced constrictive pericarditis. Associated cardiac lesions, therapy and follow-up].

OBJECTIVES: To evaluate the diagnostic and therapeutic problems that occur in managing patients with radiation-induced constrictive pericarditis. BACKGROUND: Radiation therapy of the chest and mediastinum can damage all cardiac structures, the pericardium being the most frequently involved one. It is little appreciated, however, that radiation-induced constrictive pericarditis can be associated with significant involvement of coronary arteries, myocardium and valves. METHODS: Retrospective evaluation of clinical, hemodynamic, surgical and postoperative data in 8 patients, (7 women, 1 man, aged 26-67 years, mean 44), who had received 30-50 Gy to the chest because of Hodgkin's disease, lymphoma, or breast cancer 7-23 years before the diagnosis of constrictive pericarditis. RESULTS: Six patients had symptoms related to the pericardial disease, one had angina and syncope, one was in congestive heart failure. Hemodynamic signs of constriction were obvious in 6, and were revealed by volume load in 2. All patients had mitral regurgitation, 5 had also tricuspid insufficiency and 5 had aortic regurgitation. The degree of the valvular regurgitation was > or = 3+ in four instances. Critical coronary arterial stenoses were discovered in 3 cases. The coronary ostia were involved in 5 cases (2 critical, 3 non critical). A diagnosis of restrictive cardiomyopathy was arrived at in 4 instances, always after pericardiectomy. Seven patients were operated on: there were 6 pericardiectomies, associated with either valvular surgery or myocardial revascularization or both in 3. One patient underwent myocardial revascularization only. The remaining patient is being treated medically. One patient died at surgery, two died 16 and 72 months thereafter. The remaining 5 have mild symptoms 11-60 months (mean 29) after the discharge from the hospital. CONCLUSIONS: Radiation-induced pericardial constriction is frequently associated with coronary artery disease, mostly silent, with valvular insufficiency, and with myocardial disease. Thorough cardiac evaluation in such patients is mandatory. Surgical treatment frequently uncovers an underlying restrictive myopathy that presents a serious diagnostic and therapeutic challenge.

Adult↗
PubMed1993

The effect of gestational age and fetal indomethacin levels on the incidence of constriction of the fetal ductus arteriosus.

OBJECTIVE: To determine the effects of gestational age and fetal serum indomethacin levels on constriction of the ductus arteriosus after maternal indomethacin administration. METHODS: Twenty-five pregnant Rh-sensitized patients were given a 50-mg oral dose of indomethacin 6 hours before fetal serum indomethacin levels were determined at the time of 50 diagnostic or therapeutic funipunctures. The ductus arteriosus was evaluated with Doppler ultrasound immediately before 40 of the procedures. Constriction of the ductus arteriosus was defined as a peak diastolic flow greater than 35 cm/second. Least-squares regression and multiple regression were used for statistical analysis. RESULTS: The peak diastolic velocity of the fetal ductus arteriosus after maternal indomethacin ingestion was constant at 25 cm/second before 27 weeks, increased between 27-30 weeks to a mean of 39 cm/second, and was stable thereafter (R2 = 0.35; P < .05). There was no significant correlation between constriction of the ductus and fetal serum indomethacin levels (P = .17). CONCLUSIONS: The constrictive effect of maternal indomethacin ingestion on the fetal ductus arteriosus begins as early as 27 weeks' gestation. Constriction of the ductus arteriosus is independent of fetal serum indomethacin levels.

Blood Flow Velocity↗
PubMed1996

Pericardiectomy for pericardial constriction.

Constrictive pericarditis is a pathologic condition that may lead to significant morbidity. Definitive management of constrictive pericarditis requires pericardiectomy. A retrospective review of pericardiectomy for constrictive pericarditis at the Ochsner Clinic was undertaken. Twenty-one patients (17 male, four female) underwent pericardiectomy for constrictive pericarditis between January 1969 and June 1994. Ages ranged from 15 to 66 years (mean 41.5 years). Pedal edema, dyspnea, fatigue, and chest pain were the most common symptoms. Fifteen patients had important comorbidities. Preoperative New York Heart Association (NYHA) class was I (2), II (8), III (6), IV (5). Mean preoperative catheterization data, available in 17 patients (81%), demonstrated elevated intracardiac pressures (right atrial 17.4 mm Hg, right ventricular end-diastolic 22.4 mm Hg, pulmonary artery 26.2 mm Hg, pulmonary capillary wedge 20.2 mm Hg, left ventricular end-diastolic 20.1 mm Hg). A total pericardiectomy was performed in nine patients (sternotomy 8, thoracotomy 1). Pericardiectomy limited anteriorly to the phrenic nerves was performed in 11 patients (sternotomy 9, thoracotomy 2). One partial pericardiectomy was performed through a sternotomy. Cardiopulmonary bypass was used in six patients (29%). Mean hospital stay was 12 days (preoperative 4.2, postoperative 7.67). All patients achieved NYHA Class I postoperatively. Sixteen patients were discharged in sinus rhythm. No early mortality (<30 days), or major postoperative complications were observed. Pericardiectomy for pericardial constriction can be performed safely low morbidity and mortality and can favorably impact the natural history of this debilitating condition.

Adolescent↗
PubMed1997

Decreased nitric oxide production accounts for secondary arteriolar constriction after retinal branch vein occlusion.

PURPOSE: After retinal branch vein occlusion (BVO), the arteriole crossing the occluded territories is often constricted. This constriction persists up to several weeks and is correlated with the development of extended territories of nonperfused capillaries. These are results of an investigation supporting the hypothesis that decrease in the production of nitric oxide (NO) accounts for the observed arteriolar constriction. METHODS: Preretinal [NO] was measured using an NO microprobe in the anesthetized miniature pigs, before and during the first 4 hours after experimental branch vein occlusion. Modifications of arteriolar diameter were correlated to preretinal [NO] changes. The retinal arteriolar sensitivity to constitutive NO was checked by applying preretinal puff injections of nitro-L-arginine (L-NA) after both systemic hypoxia and branch vein occlusion. RESULTS: Two hours after branch vein occlusion there was a 73.7 +/- 4% decrease in preretinal [NO] and a simultaneous 25.4 +/- 3.4% decrease in the diameter of the arteriole in the affected territory. Both persisted for at least 4 hours after branch vein occlusion. Applying a puff of L-NA to an arteriole previously dilated by systemic hypoxia induced a vasoconstriction. However, no arteriolar constriction was observed when a puff was applied to an arteriole after branch vein occlusion. CONCLUSIONS: These results show that experimental branch vein occlusion induces in the affected retina an impairment in the release of constitutive NO and an arteriolar constriction, which, in turn, contributes to the development of hypoxia in tissue and neuronal swelling and death in the inner retina.

Animals↗
PubMed1997

Characterization of a peptide endothelium-derived constricting factor EDCF.

Endothelium regulates vascular tone by the release of dilator and constrictor mediators. Among the latter, besides endothelin, an 'endothelium derived constricting factor' EDCF sensitive to cyclooxygenase-inhibitors has been described. The aim of this study was to clarify the nature of this EDCF. Eluate from porcine aortic segments or supernatants (crude extracts) of porcine aortic segments were each tested for vascular effects in a bioassay system consisting of two endothelium-denuded acceptor vessels (rabbit abdominal aorta) before or after treatment with trypsin. The donor vessels were incubated with physiological saline solution with or without treatment with cycloheximide, quinacrine or indomethacine. Ultrafiltrates and fractions of a gelfiltration of the supernatants were also tested and compared with SDS-PAGE of these extracts. Finally, porcine aortic endothelial cells (PAEC) were cultured and the supernatant compared with that of the native aortae. A vasoconstrictive factor was released from the luminal surface of the porcine aortic segments, which if infused into the rabbit aortas induced two succeeding vasoconstrictions of 15-20 min duration each (the first 20 min after the first of extract-infusion, the second after 50 min) reaching 7% amplitude of a 0.2 mumol 1(-1) norepinephrine-induced constriction. These constrictions were enhanced if the crude extract of the porcine aortae was concentrated. This constricting factor was a protein with an approximative molecular weight of 9.000 Da. The release of this factor was insensitive to cycloheximide pretreatment indicating no de novo synthesis. However, the release of the factor could be markedly (50%) depressed by pretreatment with either quinacrine or indomethacine. The factor was not released from cultured PAEC. From these results, we conclude, that besides endothelin, endothelium luminally can release another endothelium-derived constricting factor named EDCF, a peptide with a molecular weight of 9.000 Da, which is not identical to endothelium and can induce long lasting vasoconstrictions. The release or synthesis of that EDCF seems to depend on cyclooxygenase and phospholipase A2 activity. We, thus, propose the name PLA2-sensitive EDCF for that factor.

Analysis of Variance↗
PubMed1987

Three euchromatic DNA sequences under-replicated in polytene chromosomes of Drosophila are localized in constrictions and ectopic fibers.

We examined three regions of under-represented euchromatic DNA sequences (histone, Ubx, and 11 A), for their possible correlation with euchromatic constrictions in polytene chromosomes of Drosophila melanogaster. Cloned sequences were hybridized to filters and to chromosomes prepared for light microscopy. Under-represented sequences hybridized to DNA within constrictions and in ectopic fibers. In contrast, adjacent sequences that were fully endoreplicated in the Ubx and 11 A regions in polytene cells hybridized to sites just adjacent to their respective constrictions. For one region (Ubx), sequences under-represented in salivary gland cells were fully endoreplicated in fat body cells. For this particular region, the morphology of the polytene chromosomes differs between these two cell types in that the specific constriction is absent at this region in fat body polytene chromosomes, thus strengthening the correlation between under-representation and chromosome constrictions. Although all three sequences are in regions that have been classified by others as "intercalary heterochromatin," we detect no common functional or sequence organizational feature for these examples of under-represented DNA. We suggest that the lower efficiencies of the replication origins, or special regions of termination at these sites, are the primary cause of the under-replication, and that this under-replication is sufficient to confer the properties of intercalary heterochromatin.

Animals↗
PubMedDate not supplied

A new method for correcting type I and type II constricted (cup and lop) ears.

Tanzer suggested the term "constricted ear," denoting a spectrum of deformities limited to the superior third of the ear. Tanzer classified the constricted ear into three types. Type I ears have involvement of the helix, which usually is flattened. Type II ears show involvement of both the helix and the scapha. With type III ears, the auricle is rolled into a nearly tubular form that some authors regard as a form of microtia. The authors' new method for correcting the constricted ear varies in accordance with the diverse degree of deformity. The new method was used to correct constricted ears through a one-stage operation in eight type I cases. For the remaining six type 2 cases, the methods were combined with composite grafting. Most of the patients were satisfied with the final results. Therefore, the authors conclude that their approach is suitable for the treatment of type I and type II constricted ears.

Adolescent↗
PubMed1994

Cyclooxygenase inhibitors depress norepinephrine constriction of rat abdominal, but not thoracic, aorta.

Experiments were done on aortic rings (thoracic and abdominal) from young and retired breeder Lewis and Sprague-Dawley male rats. Constriction responses to norepinephrine, 5-hydroxytryptamine (5-HT), and prostaglandin F2 alpha, were done +/- the cyclooxygenase blockers, indomethacin or mefenamic acid. Indomethacin significantly depressed norepinephrine constriction in abdominal (but not thoracic) aorta of all groups. In additional studies of abdominal aorta from Lewis retired breeders, indomethacin and mefenamic acid depressed norepinephrine (but not 5-HT or prostaglandin F2 alpha) construction. Furthermore, indomethacin depressed norepinephrine constriction in vessels denuded of endothelial cells. The thromboxane receptor antagonist SQ 29548 did not alter norepinephrine constriction. Thus, in rat abdominal aorta, norepinephrine constriction is mediated by a constrictor prostanoid of vascular smooth muscle origin that is not thromboxane A2.

Adrenergic alpha-Antagonists↗
PubMed1992

Pupillary constriction in response to light in rodents, which does not depend on central neural pathways.

We show here that the widely held belief that reflex constriction of the mammalian pupil in response to light depends exclusively upon neural pathways between eye and brain is in need of revision. We investigated the response of the pupil to light in dark-adapted rodents (golden hamsters; hooded rats; albino rats) subjected to a variety of surgical and pharmacological interventions designed to destroy or block all of the neural pathways and structures through which the reflex could be mediated. The interventions included bilateral intraorbital optic nerve section, or unilateral intracranial optic nerve section with enucleation of the contralateral eye, combined in some cases with bilateral removal of the superior cervical ganglia and/or pinealectomy; topical application of atropine; intraocular injection of tetrodotoxin (TTX). Golden hamsters and hooded rats, but not albino rats, retained an effective constriction of the pupil in response to light after all of these interventions, although the constriction was less and slower than in normal animals. These findings show that hamsters and hooded rats have both a neurally mediated fast light reflex that can be eliminated by severing connections between eye and brain, by blockade of cholinergic transmission to iris smooth muscle, and by blockade of action potentials by TTX; and a local, slower constriction in response to light, which remains after all these procedures. We have also confirmed previous observations of Bito and Turansky (1975) that pupillary constriction in response to light occurs in isolated in vitro anterior chamber preparations of hamster and hooded rat eyes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Cocaine and benzoylecgonine constrict cerebral arteries by different mechanisms.

This study was designed to determine possible mechanisms underlying the vasoconstrictor activity of cocaine and its principal metabolite, benzoylecgonine (BE) in cat isolated cerebral arteries. The arteries constricted significantly in response to single doses of cocaine, BE and norepinephrine (NE; (P < 0.05). After 6-OHDA treatment to remove adrenergic nerve endings, NE-induced constrictions were essentially unchanged from those before treatment. Denervated arteries exposed to cocaine dilated significantly (P < 0.05) but those exposed to BE constricted as much as before denervation. Following exposure to prazosin and yohimbine, arterial constrictions to NE and cocaine were significantly reduced from control (P < 0.05) but the BE-induced constriction was unchanged. Ryanodine eliminated the cocaine-induced contraction (P < 0.05) whereas verapamil eliminated the BE response (P < 0.05). These data suggest that while cocaine's vasoconstrictor action may be significantly mediated through adrenergic transmission, BE may act through a mechanism involving calcium (Ca2+) channels. Cocaine levels peak and decline in the body more rapidly than BE levels which can remain detectable for days. This study suggests there may also be different pharmacological mechanisms as well as temporal differences underlying the vasoreactivity of these two substances. Our findings may have implications for pharmacological management of cocaine-induced toxic vascular events.

Animals↗
PubMed1989

Epicardial coronary artery constriction with intravenous ethanol.

Although in vitro studies have demonstrated ethanol-induced coronary artery constriction, in vivo reports suggest an ethanol-related coronary dilator effect with increases in coronary blood flow. The principal difference in these studies is the demonstration of epicardial coronary constriction with ethanol, while dilation is described only in resistance vessels. Clinical studies have noted evidence of myocardial ischemia following ethanol ingestion in patients with coronary artery disease, suggesting ethanol-related constriction of diseased epicardial coronary arteries. This study hypothesized that intravenous ethanol would constrict canine epicardial coronary arteries while producing arteriolar resistance vessel dilatation. Ten closed-chest mongrel dogs weighing 24 +/- 1 kg (mean +/- SEM) were given 8 g of ethanol intravenously over 30 min. Left anterior descending and circumflex proximal artery diameters were measured by quantitative coronary angiography; myocardial flow was measured by Xenon washout, and myocardial flow distribution was measured with radioactive microspheres. Baseline proximal left anterior descending and circumflex artery areas were 6.3 +/- 0.5 and 5.8 +/- 0.4 mm2, respectively. Up to 30% left anterior descending and circumflex proximal artery narrowing was noted at 60 and 90 min following ethanol infusion. The constriction was reversed with nitroglycerin. There was a decrease in left anterior descending artery flow but no change in circumflex artery flow at 60 min. Blood ethanol level varied from 520 micrograms/ml initially to 205 micrograms/ml 90 min after the infusion terminated (intoxication = 1500 micrograms/ml). These data suggest that ethanol has significant vasoconstrictor action in vivo on epicardial coronary arteries.

Alcoholism↗
PubMed1995

Time-course changes in gastric mucosal blood perfusion following portal vein constriction in rats.

BACKGROUND/AIMS: Gastric mucosal blood flow is increased in all experimental models of chronic portal hypertension, when portosystemic shunting and the hyperdynamic circulation are fully developed. However, some controversy exists concerning the time course of this event. This study was undertaken to investigate the chronological changes in gastric mucosal blood perfusion during the first 7 days after partial portal vein constriction. METHODS: Portal hypertensive and sham operated animals were studied. Gastric mucosal blood flow was measured by hydrogen-gas clearance and gastric oxygen and hemoglobin content by reflectance spectrophotometry, prior to and immediately after partial portal vein constriction, and 1, 2, 7 and 15 days after induction of portal hypertension. RESULTS: Immediately after partial portal vein constriction, gastric mucosal blood flow and gastric oxygen were significantly decreased by 27% and 32% respectively, and gastric hemoglobin significantly increased by 19%. On day 1, gastric mucosal blood flow was increased in both portal hypertensive and sham operated rats. However, while this parameter returned to normal in sham operated rats, it remained high on days 2, 7 and 15 in portal hypertensive rats. In portal hypertensive rats, gastric oxygen values were not significantly different from those in sham operated animals, but hemoglobin tended to increase with development of portal hypertension, being significantly higher than in sham operated rats at days 2 and 7. Similar results were obtained when analyzing gastric mucosal blood perfusion 2 and 7 days after two-staged total portal vein constriction. CONCLUSIONS: Increased gastric mucosal blood perfusion is present in portal hypertensive rats from the first day after partial portal vein constriction. The lack of significant differences in all parameters on day 1 between portal hypertensive and sham operated rats is probably related to an increased mucosal blood perfusion related to surgery.

Analysis of Variance↗
PubMed1993

Diltiazem and regional left ventricular function during graded coronary constriction and propofol anesthesia in the dog.

Although calcium channel blockers may preserve function in ischemic myocardium, they may also produce myocardial depression and dysfunction in the presence of decreased coronary flow. This study was designed to examine the issue of possible protection afforded by diltiazem against ischemia-induced myocardial dysfunction during propofol anesthesia. In eight anesthetized and ventilated dogs, regional myocardial (ultrasonic crystals in both left anterior descending [LAD] and left circumflex [LC] perfusion areas) and global ventricular function were evaluated during progressively severe degrees of myocardial ischemia (LAD constriction) before and after intravenous diltiazem (150 micrograms/kg). As coronary flow decreased, heart rate increased, and arterial and coronary perfusion pressures, left ventricular dP/dt, and cardiac output decreased. Systemic vascular resistance was unaffected. Diltiazem without coronary constriction increased heart rate, and decreased diastolic arterial pressures, left ventricular (LV) end-diastolic, coronary perfusion pressures, LV dP/dt max, LAD coronary blood flow, stroke volume, and cardiac output. At all levels of coronary constriction following diltiazem, there were decreases in systolic and diastolic arterial pressures, stroke volume, cardiac output, LV dP/dt, and coronary perfusion pressure. Heart rate increased at critical coronary constriction, and then remained constant relative to the prediltiazem state. The regional muscle effects of the reductions in coronary flow in the LAD perfusion territory included decreased systolic shortening and increased postsystolic shortening before and after diltiazem. Diltiazem did not alter the magnitude of the alterations in systolic or postsystolic shortening brought about by coronary constriction. No changes occurred in the LC area.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Intravenous↗
PubMed2005

Efficacy of peroxisome proliferative activated receptor (PPAR)-alpha ligands, fenofibrate, on intimal hyperplasia and constrictive remodeling after coronary angioplasty in porcine models.

Constrictive remodeling and intimal hyperplasia play a prominent role in restenosis after angioplasty. It has been reported that the severity of constrictive remodeling and intimal hyperplasia correlate with adventitial angiogenesis and inflammation. Experimental evidence indicates that inflammation participates in angiogenesis, and therefore inhibition of inflammation may impair neovascularization. We tested whether fenofibrate, peroxisome proliferative activated receptors (PPAR)-alpha specific ligand, inhibits the early inflammation, adventitial angiogenesis, constrictive remodeling and intimal hyperplasia after angioplasty using porcine coronary arteries. Fenofibrate was tested in vivo, in 30 coronary arteries of 10 pigs (1g/day, orally) and was compared to placebo. Quantitative intravascular ultrasound and histopathologic assessment showed that fenofibrate increased lumen (6.28 mm(2) versus 5.15 mm(2)), vessel area (7.34 mm(2) versus 6.69 mm(2)) and inhibited constrictive remodeling. Inflammatory cell infiltration was evaluated with scanning electron microscopy 3 days after angioplasty and was significantly decreased in the treated vessels compared to control. Adventitial angiogenesis 3 days after angioplasty was significantly reduced in the injured vessels derived from the fenofibrate treated group compared to placebo. In conclusion, pharmacological activation of PPAR-alpha inhibited constrictive remodeling and neointimal hyperplasia after angioplasty through inhibition of inflammation and adventitial neovascularization.

Angioplasty, Balloon, Coronary↗
PubMed2004

Effect of a graded single constriction of the rat sciatic nerve on pain behavior and expression of immunoreactive NPY and NPY Y1 receptor in DRG neurons and spinal cord.

In the present study, the rat sciatic nerve was constricted to varying degrees using only one ligature with a very thin polyethylene sheath placed between nerve and ligature thread. Complete nerve transection was studied for comparison. With a 40-80% constriction of the nerve we observed allodynia to a similar extent as in the so-called Bennett model based on four loose ligatures. We also monitored changes in the expression of neuropeptide Y (NPY) and the NPY Y1 receptor (Y1R) in the lumbar 4-5 dorsal root ganglia (DRG) and dorsal horn and found upregulation of NPY and downregulation of the Y1R in DRG neurons after injury. These results indicate that similar peptide and receptor changes occur in this model as after axotomy and in other nerve injury models, although the immunohistochemical and behavioral changes seem to be dependent on the degree of constriction of the nerve. Thus, it seems relevant to monitor the degree of constriction when evaluating pain and other post-injury events. The possibility that some of the changes in NPY-ergic neurotransmission are related to the generation of allodynia is discussed; as well as the possibility to use this mononeuropathic model based on a single ligature nerve constriction (SLNC) as a complementary approach to other widely used pain models.

Animals↗
PubMed2004

Rapid constriction of lipid bilayers by the mechanochemical enzyme dynamin.

Dynamin, a large GTPase, is located at the necks of clathrin-coated pits where it facilitates the release of coated vesicles from the plasma membrane upon GTP binding, and hydrolysis. Previously, we have shown by negative stain electron microscopy that wild-type dynamin and a dynamin mutant lacking the C-terminal proline-rich domain, DeltaPRD, form protein-lipid tubes that constrict and vesiculate upon addition of GTP. Here, we show by time-resolved cryo-electron microscopy (cryo-EM) that DeltaPRD dynamin in the presence of GTP rapidly constricts the underlying lipid bilayer, and then gradually disassembles from the lipid. In agreement with the negative stain results, the dynamin tubes constrict from 50 to 40 nm, and their helical pitch decreases from approximately 13 to 9.4 nm. However, in contrast to the previous results, examination by cryo-EM shows that the lipid bilayer remains intact and small vesicles or fragments do not form upon GTP binding and hydrolysis. Therefore, the vesicle formation seen by negative stain may be due to the lack of mobility of the dynamin tubes on the grid during the GTP-induced conformational changes. Our results confirm that dynamin is a mechanochemical enzyme and suggest that during endocytosis dynamin is directly responsible for membrane constriction. In the cell, other proteins may enhance the activity of dynamin or the constraints induced by the surrounding coated pit and plasma membrane during constriction may cause the final membrane fission event.

Animals↗
PubMed2006

Can a fluoroscopic estimation of pharyngeal constriction predict aspiration?

BACKGROUND: The pharyngeal constriction ratio (PCR) is a ratio of pharyngeal area measured in lateral fluoroscopic view at the point of maximum pharyngeal constriction during the swallow to the pharyngeal area measured with the bolus held in the oral cavity. We hypothesize that the PCR may represent a surrogate measure of pharyngeal strength. OBJECTIVE: To investigate the relationship between the PCR and aspiration. STUDY DESIGN AND SETTING: Data from a computerized clinical database of individuals undergoing a videofluoroscopic swallow evaluation at a tertiary academic swallowing center was acquired. RESULTS: Two hundred sixty videofluoroscopic studies were abstracted. The mean PCR was 0.32 (+/- 0.02) for individuals who aspirated and 0.20 (+/- 0.02) for individuals who did not (P < 0.001). In a multiple logistic regression analysis, the PCR was significantly associated with the prevalence of aspiration (P < 0.01). Individuals with a PCR greater than 0.25 were 3 times more likely to aspirate (95% CI = 1.7, 5.1). CONCLUSIONS: The pharyngeal constriction ratio is associated with the presence of aspiration on fluoroscopy. Before the PCR can be used as a surrogate measure of pharyngeal constriction, correlation with pharyngeal manometry will be necessary. SIGNIFICANCE: The pharyngeal constriction ratio is associated with the presence of aspiration on fluoroscopy. EBM RATING: B-3b.

Aged↗